Ascorbic acid concentration in rabbit vitreous measured by microdialysis with HPLC-electrochemical detection before and after vitreous surgery

Abstract

Microdialysis with high performance liquid chromatography and electrochemical detection (HPLC-ECD) was used to measure ascorbic acid (AA) concentrations in rabbit vitreous before and after vitrectomy. A cellulose microdialysis probe was implanted in the vitreous humor, and after stabilization, AA measurements were made daily over a 10 day period. The effect of removing two-thirds of the vitreous by vitrectomy was examined. The effect of triamcinolone acetonide (TA) was evaluated in four groups of rabbits: Group 1, sub-tenon TA (20 mg) alone; Group 2, intravitreous TA (4 mg) alone; Group 3, sub-tenon TA (20 mg) after vitrectomy, and Group 4, intravitreous TA (4 mg) after vitrectomy. The results showed that the AA concentration after vitrectomy was significantly lower from days 2 to 10 with a maximum reduction of 49.5% (P < 0.005) on day 7. No significant changes in the AA level was observed in Groups 1 and 2, a mild recovery of AA concentration reduction after vitrectomy was detected in Group 3. The highest recovery of the AA concentration reduction was observed in Group 4. The attenuating effect of TA treatment on the reduction of AA in the vitreous after vitrectomy was significant. This attenuating effect of the TA may be due to prevention of the disruption of the blood-aqueous barrier by its anti-inflammatory action.

A Hydrogel Vitreous Substitute that Releases Antioxidant

“…Vitamin C has been shown to readily degrade in water due to light exposure, pH, level of dissolved oxygen, and the presence of metal ions . However, the normal in vivo concentration of vitamin C in the vitreous is 1–2 m m , which suggests that there is a rapid turnover of vitamin C in vivo. More research is needed to determine the ideal release and retention rates of vitamin C to prevent the lens from developing cataract due to oxidative damage; vitamin C encapsulation will be explored to protect the antioxidant.…”

“…The rapid release of vitamin C within the first 12 h (Figure ) from these hydrogels might be beneficial in consuming the excess oxygen in the eye during and immediately following surgery, minimizing lens exposure to oxidative damage. The concentration of vitamin C has been recently shown to decrease after vitrectomy due to the removal of the vitreous, which naturally holds a large amount of vitamin C . The rapid release of vitamin C from the hydrogel might replenish this depletion of vitamin C while new vitamin C is being generated by the ciliary body epithelium and retinal epithelium to the normal level, which is thought to take several weeks .…”

Antioxidants and the Integrity of Ocular Tissues

“…Also, ascorbate can act as a pro-oxidant in the presence of excessive concentrations of ions Fe +3 and Cu +2 [6, 7, 14]. Ascorbate was detected in cornea [31], aqueous humor [32, 33], lens [34], vitreous humor [35], and retina [29]. …”

Determination of Vitamin C (Ascorbic Acid) Using High Performance Liquid Chromatography Coupled with Electrochemical Detection

“…Thus, there is a need of analytical procedures able to not only monitor AA content in agricultural and food products, but also in body liquids and tissues [11]. Authors also paid their attention at detection of AA in blood serum [12-15]. …”